Conventionally, tires mounted on a vehicle are undergone so-called rotation to exchange the mounted positions every time a predetermined distance is traveled in order to prevent uneven wear of a tread rubber. And, when a tire has its tread rubber worn to some extent, it is disposed or retreaded by replacing with a new tread rubber.
It is known that the tire is deteriorated by not only the worn out of the tread rubber, but also a damage by an external factor of a tire casing (hereinafter called as casing) other than the tread rubber, a crack with a lapse of time, etc. And, since the deteriorated state of the tread rubber due to wear, a flaw or the like can be checked visually, its management is relatively easy. On the other hand, the deteriorated state of the casing is not grasped easily, and, for example, PTL 1 discloses a technology to predict the deterioration of the casing with time.
According to PTL 1, a life (service life) of the casing can be predicted to some extent, but a progress of wear of the tread rubber and that of deterioration of the casing with time are different depending on the mounted positions of tires on the vehicle, and a progress of deterioration of each tire due to wear of the tread rubber and a progress of deterioration of the casing with time do not always match. Therefore, it is not easy for the user to grasp the state of the tires including the above and to manage the tires.